Question

sea urchins can overpopulate and cause environmental damage unless they are kept in check by predators. which of these species is a keystone species that feed on sea urchins? sea otters hermit crabs

Explanation:

In marine ecosystems, sea otters are known keystone species. They feed on sea urchins. By controlling sea urchin populations, sea otters prevent overgrazing of kelp forests (by sea urchins), maintaining the health of the ecosystem. Hermit crabs do not primarily feed on sea urchins.

Answer:

sea otters